Groups of neuronal cells in localized regions of the brain, for example of the thalamus and the basal ganglia, are pathologically active, for example, excessively synchronously active in patients with neurological or psychiatric illnesses, for example, Parkinsons's disease, essential tremors, dystonia or obsessive compulsive disorders. In this case a large number of neurons form synchronous action potentials, this means that the concerned neurons trigger excessively synchronously. In contrast to this the neurons of healthy patients trigger qualitatively differently in these brain regions, for example, in an uncorrelated manner.
For Parkinsons's disease the pathologically synchronous activity changes the neuronal activity in different brain regions, for example, in areas of the cerebral cortex, such as the primary motor cortex. In this respect the pathological synchronous activity in the region of the thalamus and the basal ganglia, for example, force their rhythm onto the cerebral cortex regions, so that muscles controlled by these regions finally develop the pathological activity, for example, a rhythmic tremor.
Neurological and psychiatric diseases with excessively strongly pronounced neuronal synchronization have up until now been treated—on failure of drug therapy—by means of electrical brain stimulation.